Supporting device for hand tools



Oct. 3, 1967 G. L. GRANSTEN SUPPORTING DEVICE FOR HAND TOOLS Filed July so. 1965 INVENTOR GUNNAR LENNARTGRANSTHV ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE A telescopic resilient support for hand tools having a tubular barrel which is closed at its lower end by a base and houses a telescopically displaceable support rod which is provided with a plunger at its lower end, and with a mounting for the hand tool at its upper end. A variable volume air chamber is defined by the bore of the barrel, the base and the plunger. A non-return valve allows atmospheric air to enter the air chamber on manual lifting of the support rod and a second non-return valve allows the air in the air chamber to enter an air reservoir on depression of the support rod. A third valve is operable to place the air chamber and the air reservoir in open communication with each other so that the plunger, the support rod and the hand tool are supported on an air cushion in the air chamber and the air reservoir.

This invention relates to supporting devices for hand tools and is more particularly concerned with a device for resiliently supporting a hand tool.

A considerable effort is often required to support a hand tool, such as a grinding, boring or riveting machine, on a variable level without facilities when operating on walls or ceilings, for example. The devices hitherto used for relieving the weight of hand tools suffer from the disadvantage that they are heavy and unwieldy. Moreover, they often require a separate power source.

The invention has for its object to provide an easily handled supporting device for hand tools which device is independent of separate power sources and by means of which device a hand tool can be supported on a variable level and resiliently raised and lowered with little effort.

This object is achieved by a supporting device of the type indicated, comprising a tubular barrel which in its operating position is at least fairly upright and which is closed at its lower end by an end piece, a supporting rod inserted from above into the barrel and having on its upper end protruding from the barrel a socket for a hand tool and having on its lower end a plunger, a first nonreturn valve adapted to permit air to pass into a variable volume air chamber defined between the plunger and the end piece when the plunger is displaced upwards in the barrel, a second non-return valve adapted to permit air compressed in the air chamber to pass into a reservoir for compressed air, and a third valve operable to place the reservoir and the air chamber in free communicatoin with each other. 1

' Preferably, the first nonreturn valve is positioned and arranged so as to prevent air from entering into the air chamber until the plunger has been displaced upwards a predetermined distance in the barrel and the effective cross-sectional area of the air chamber is sufficiently 'large to cause a force larger than the weight of the whole device except the support rod and the plunger to be required to displace the plunger upwards in the barrel more than the said predetermined distance. This makes it possible to lift and move the supporting device using the hand tool as a handle after the plunger has been moved down to its lowermost position. When the plunger is to be moved upwards in the barrel so as to permit air to pass 3,345,021 Patented Oct. 3, 1967 into the air chamber the barrel may be withheld on the floor or supporting surface while the hand tool is lifted.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing:

FIGURE 1 is an elevation of the supporting device together with a hand tool;

FIGURE 2 is an enlarged sectional view of the supporting device shown in FIGURE 1, a length of the barrel and support rod being broken away.

The supporting device 10 is intended to be at least fairly upright when it is in its operating position. However, the term fairly upright is to be taken as including a consderable inclination, say up to 4045, to the vertical.

The supporting device comprises a tubular barrel 11 having its upper end slightly below the lowest level desired. The lower end of the barrel 11 is closed by an end piece 12 made in two parts 12A and 128 secured to each other by bolts (not shown). The end piece 12 is connected to a base 13 by means of a rod 14 which is axially slidable in a blind bore 15 in the lower part 12B of the end piece 12. In the embodiment shown, the base 13 is constituted by a plate 16 and a peg 17 to be forced down into a supporting surface, for example, a floor or a board. The base may also be a flat plate pivotally connected to the rod 14.

A tubular support rod 18 is inserted from above into the barrel 11 through a sealing and guiding device 19 at the upper end of the latter. The upper end of the support rod 18 protrudes from the barrel 11 and is provided with a socket 20 to which a hand tool 21 (FIGURE 1) is pivotally connected. To the lower end of the support rod 18 there is secured a tubular plunger 22 having a first nonreturn valve 23 adapted to permit air to pass downwards through the support rod into an air chamber 24 between the plunger 22 and the end piece 12. The air passes through an inlet 25 in the socket 20 and through a filter 26 before it reaches the plunger 22.

When in its lowermost position the tubular plunger 22 is sealingly engaged over a tube 27 extending axially upwards from the upper part 12A of the end piece 12. A sealing ring 28 ensures a gas-tight seal between the tube 27 and the plunger 22. The upper end portion 29 of the tube 27 is tapered so that the sealing between the tube and the plunger ceases gradually when the sealing ring 28 is displaced along the upper end portion 29.

In the upper part 12A of the end piece 12 a second nonreturn valve 30 is inserted into an axial bore 31 connected to a transverse channel 32. The channel 32 communicates fr'eely, namely through an opening 33 in the barrel 11, with a reservoir 34 for compressed air which reservoir 34 sealingly surrounds a length of the barrel 11. The channel 32 also communicates freely with another axial bore 35 which in turn communicates with the bore of the tube 27 and into which a third valve 36 is inserted. The valve 36 is spring-biased sufficiently to normally make it impossible for the air pressure in the reservoir 34 to open it. However, it is not biased so hard that it cannot be kept open by upper end face of the rod 14 when the supporting device 10 rests on the base 13. The rod 14 is biased downwards by a compression spring 37 ensuring that the rod 14 is displaced downwards when the barrel 11 is raised. The force of the spring 37 is larger than the weight of the barrel 11 and the parts secured thereto. The downward movement of the rod 14 in the end piece part 12B is limited by an abutment 38 while the upward movement is limited by the bottom 39 of the blind bore 15.

The upper part 12A of the end piece 12 is also provided with a fourth valve 40 which when open communicates the air chamber with atmosphere. The valve 40 is spring-biased so hard that it normally cannot be opened by the air pressure in the air chamber 24. Its valve stem 41 projects slightly above the upper face of the end piece part 12A and when the plunger 22 is in its lowermost position it keeps the valve stem 41 displaced downwards so as to keep the valve 40 open. The purpose of the valve 40 will be explained below.

Briefly, the operating principle of the supporting device is that by means of the support rod 18 and the nonreturn valve 30 an air pressure is built up in the reservoir 34 which is sufiicient to support the plunger 22, the support rod 18 and the hand tool 21 thereon when it acts on the plunger through the channel 32, the axial bore 35 and the bore of the tube 27.

In detail the operation of the supporting device 10 is as follows:

When the hand tool 21 and the support rod 18 are pulled upwards with respect to the barrel 11 a subatmospheric pressure is created in the air chamber 24. The effective cross-sectional area of the air chamber 24 is dimensioned so as to make the force required to pull the plunger 22 upwards in the barrel 11 beyond the upper end of the tube 27 larger than the weight of the barrel 11 and the parts secured thereto. Therefore, when the hand tool 21 and the support rod 18 and the plunger 22 secured thereto are raised also the barrel 11 and its end piece 12 will be raised. The rod 14 will then be displaced down- Wards under the influence of gravity and of the spring 37. Consequently, the valve 36 closes to block the connection between the reservoir 34 and the air chamber 24.

To pull the plunger 22 upwards beyond the tube 27 it is necessary to hold the barrel 11 so as to prevent it from moving with the plunger. This can be done by pressing the base 13 downwards by means of a foot. When the sealing ring 28 slides over the tapered end portion 29 of the tube 27, the nonreturn valve 23 is opened under the influence of the subatmospheric pressure in the air chamber 24. Then air can pass through the plunger 22 and into the air chamber 24. The plunger is forced down by the support rod 18 to compress the air in the air chamber 24. The compressed air flows over the non-return valve 30 and into the reservoir 34. The valve 36 will also open when the plunger 22 is forced downwards since the barrel 11 and the end piece 12 will be lowered until the upper end of the rod 14 opens the valve 36, but this has no effect since the nonreturn valve 23 of the plunger 22 is closed.

The support rod 18 is reciprocated until the pressure in the reservoir 34 is sufficient to support the hand tool 21 when it acts on the plunger 22. It will be appreciated that the hand tool 21 can be resiliently lowered and raised with little effort since the air below the plunger and in the reservoir forms an air spring. The force biasing the plunger 22 upwards can easily be increased by pumping more air into the reservoir 34 or decreased by blowing off air from the reservoir through a valve 42. Besides the valve 42 the reservoir 34 is provided with a safety valve and a draining valve for condensate (not shown).

When the plunger 22 is pushed down to its lowermost position it opens the valve 40 to communicate the air chamber 24 with atmosphere and blow out remaining compressed air from the air chamber. Thus, the plunger 22 will come to rest on the end piece 12 without being acted on by an upwardly directed air pressure (except, of course, the air pressure acting on an area equal to the small net cross-sectional area of the tube 27 since the valve 36 is open). The supporting device 10 and the hand tool 21 can, therefore, be safely put aside leaning against a wall, for example. The valve 40 may also serve as a safety valve for limiting the pressure in the reservoir 34.

Since the effective cross-sectional area of the air chamber 24 is dimensioned so as to make the force required to pull the sealing ring 28 of the plunger 22 upwards beyond the upper end portion 29 of the tube 27 larger than the weight of the barrel 11 and the parts secur d thereto the supporting device 10 as a whole can be lifted and moved to another place using the hand tool 21 as a handle.

Although only one embodiment of the invention has been illustrated and described in detail, it is to be understood that the invention is not limited thereto. Various changes can be made without departing from the spirit and scope of the invention as expressed in the appended claims.

What is claimed is:

1. A device for resiliently supporting a hand tool on a variable level, comprising:

(a) a tubular barrel closed at one end by an end piece;

(b) a support rod telescopically displaceable in said barrel, one end of said support rod protruding from the other end of said barrel and having means for securing to an associated hand tool;

(c) a plunger mounted on the other end of said support rod;

(d) an air chamber defined within said barrel between said end piece and said plunger;

(e) an air inlet passage connecting said air chamber to the atmosphere;

(f) a compressed air reservoir;

(g) first and second air transfer passages communicating said air chamber with said air reservoir;

(h) first valve means in said air inlet passage to permit atmospheric air to enter said air chamber in response to manually pulling said support rod and plunger away from said end piece;

(i) second valve means in said first air transfer passage to permit air to pass from said air chamber into said compressed air reservoir in response to pushing said support rod and plunger towards said end piece; and

(j) third valve means in said second air transfer passage operable to open said second air transfer passage to place said compressed air reservoir and said air chamber in open communication with each other,

(k) whereby said plunger, support rod and hand tool are resiliently supported by the compressed air contained in said reservoir and said air chamber.

2. A device as in claim 1 further including a base member mounted at one end of said tubular barrel.

3. A device as set forth in claim 1 wherein:

(a) said air inlet passage opens into said air chamber through an opening which is covered until said plunger has been displaced a predetermined distance away from said end piece; and

(b) wherein the effective cross-sectional area of said air chamber is sufficiently large to cause a force greater than the weight of the entire device except said support rod and plunger to be required to overcome the suction force acting on said plunger and pull said plunger said predetermined distance away from said end piece.

4. A device as set forth in claim 1 wherein:

(a) said air inlet passage comprises an axial bore in said plunger;

(b) said second air transfer passage comprises a tubular member protruding from said end piece towards said plunger, said plunger being sealingly engageable over said tubular member; and

(c) wherein the effective cross-sectional area of said air chamber is sufliciently large to cause a force greater than the weight of the entire device except said support rod and plunger to be required to overcome the suction force acting on said plunger and pull said plunger away from said end piece sufiiciently to disengage it from said tubular member.

5. A device as set forth in claim 1 wherein:

(a) said third valve means comprises a valve body which is spring biased in a valve closing direction and is provided with an actuating member extending in said valve closing direction towards said base member; and

(b) said third valve means including an axially displaceable rod connecting said end piece to said base member and engageable with said actuating member to open said third valve means.

6. A device as set forth in claim 1 wherein:

-(a) a fourth valve means is positioned in an air passage connecting said air chamber to atmosphere;

(b) said fourth valve means comprising a valve body which is spring biased in a valve closing direction and provided with an actuating member extending in said valve closing direction and protruding into said air chamber through said end piece;

(0) whereby said fourth valve means is displaced by said plunger to an open position When said plunger is resting on said end piece.

7. A device as set forth in claim 1 wherein said com- 5 pressed air reservoir surrounds a length of said barrel,

a wall portion of said reservoir being clamped to an adjacent end of said barrel.

References Cited UNITED STATES PATENTS 15 JOHN PETO, Primary Examiner. 

1. A DEVICE FOR RESILIENTLY SUPPORTING A HAND TOOL ON A VARIABLE LEVEL, COMPRISING: (A) A TUBULAR BARREL CLOSED AT ONE END BY AN END PIECE; (B) A SUPORT ROD TELESCOPICALLY DISPLACEABLE IN SAID BARREL, ONE END OF SAID SUPPORT ROD PROTRUDING FROM THE OTHER END OF SAID BARREL AND HAVING MEANS FOR SECURING TO AN ASSOCIATED HAND TOOL; (C) A PLUNGER MOUNTED ON THE OTHER END OF SAID SUPPORT ROD; (D) AN AIR CHAMBER DEFINED WITHIN SAID BARREL BETWEEN SAID END PIECE AND SAID PLUNGER; (E) AN AIR INLET PASSAGE CONNECTING SAID AIR CHAMBER TO THE ATMOSPHERE; (F) A COMPRESSED AIR RESERVOIR; (G) FIRST AND SECOND AIR TRANSFER PASSAGES COMMUNICATING SAID AIR CHAMBER WITH SAID AIR RESERVOIR; (H) FIRST VALUE MEANS IN SAID AIR INLET PASSAGE TO PERMIT 